| Selenium was first identified in 1817 by the Swedish chemist Jakob Berzelius (1779-1848) after analyzing an impurity that was contaminating the sulfuric acid (H2SO4). Berzelius and his colleague Johann Gottlieb Gahn (1745-1818) were studying a method of producing sulphuric acid in lead cameras "We observed residues of a substance, partially red and partially light-brownish, with a very intense scent in the bottom of the camera. Such scent, according to Klaproth, is the sign of presence of tellurium, so at first we thought it was tellurium. Gahn noticed that in mines of Falun, were sulphur is collected, similar scent of tellurium is also often felt. Interested and hoping to discover a new metal, I commenced to investigate substance of the residues. However, more careful attempts to separate tellurium, comparing with the analysis of burnt ores from Falun, revealed that there were no residues of this element, in spite of its identical properties. It was a new substance and, following the identity of properties, was given the name Selenium, term that derives from the Greek ∑εληνη (Moon), since Klaproth had named tellurium for the Earth." |
Average crustal abundance is 1.4x10-5% by mass, in sea waters 4x10-3mg/l. Over 50 selenium minerals are known such as native selenium, berzelianite (copper selenide), naumannite Ag2Se, chalcomenite CuSeO3 x 2 H2O. Selenium concentration in pyrite (iron sulphide), galena (lead sulphide), bismuthinite (bismuth sulphide) and other sulphides, as well as in volcanic sulphur, reaches several per cents.
Selenium is most commonly produced from selenide in many sulphide ores, such as those of copper, Silver, or lead.
Selenium is a very rare trace element. It history in the Earth& |